1. Field of the Invention
The present invention relates to a circulation apparatus for coolant, provided in a vehicle for circulating coolant.
2. Description of the Related Art
Recently, there has been an increasing demand for introducing a low-pollution vehicle and alternative energy vehicle, accompanied with demands for improving the air environment and environmental problems. As a strong candidate for the alternative energy vehicle, there is the hybrid vehicle which uses an electric motor together with an engine.
A hybrid vehicle is driven by an engine at the time of high speed driving, and is driven by a drive motor with a battery as a power source at the time of low speed driving. The battery is charged by driving an electric power generation motor at the time of engine driving.
Since a plurality of drive sources are provided in this manner, then with the hybrid vehicle, cooling systems must be provided for each of the drive sources. That is to say, it is necessary to provide a coolant circulation apparatus for circulating coolant between a radiator and an engine as with the conventional engine to thereby cool the engine. Moreover, the drive motor is cooled by providing a coolant circulation apparatus for drive motor coolant. Furthermore, since it is necessary to cool the electric power generation motor while this is bring driven, then a coolant circulation apparatus is also required for this. Here with the drive motor and the electric power generation motor, the temperature must be maintained at less that around 65xc2x0 C.
Moreover, in the case where a high temperature battery such as a lithium ion battery is used as the battery, then it is desirable to control the temperature to around 85xc2x0 C. to improve the electric power generation and storage efficiency.
Incidentally, when using the drive motor and the electric power generation motor the cooling (control) temperature for the battery differs. Consequently, in addition to providing a cooling system which includes a radiator (referred to hereunder simply as a cooling system) for engine cooling, it is necessary to also provide respective separate cooling systems, one for cooling the drive motor and the electric power generation motor, and one for cooling the battery. Moreover, in the case where for example an intercooler is provided as engine equipment, then cooling of this must also be considered. Therefore, the cooling equipment is increased together with an increase in weight, so that there is the problem of mounting in a vehicle where miniaturization is required.
In view of the above situation, it is an object of the present invention to provide a circulation apparatus for coolant in a vehicle, which realizes miniaturization and weight reduction of equipment.
With the circulation apparatus for coolant in a vehicle of the present invention, then with a circulation apparatus for coolant in a vehicle incorporating; a radiator for cooling coolant, and an apparatus to be cooled, with a coolant circulated between the radiator and the apparatus to be cooled, the coolant is circulated between a single radiator and a plurality of apparatus to be cooled.
In a hybrid vehicle, for the apparatus to be cooled, then apart from the engine there is the drive motor, the intercooler, and the exhaust gas re-circulation (referred to hereunder as EGR) unit. However, these are not all used at the same time. For example, considering the intercooler and the drive motor, the intercooler is only used at the time of engine driving, and hence the intercooler and the drive motor are not used at the same time. That is to say, even if the cooling system for intercooler cooling and the cooling system for drive motor cooling are provided separately, since these cooling systems are not used at the same time, then cooling of the two can be performed by a single cooling system if the cooling systems are common for both the intercooler and the drive motor.
That is, the individually provided radiators can be combined and cooling performed in a centralized manner with one radiator, thereby minimizing the capacity of the radiators. Consequently, even if as with the present invention the construction is such that the coolant is circulated between a plurality of apparatus to be cooled and a single radiator, the weight and volume of the radiator can be reduced without reducing the cooling capacity.
More specifically, with the apparatus to be cooled as the engine, the drive motor, and the engine equipment, a first radiator is provided for engine cooling, and a second radiator is provided for drive motor and engine equipment cooling. For the engine equipment there is an intercooler, and/or an exhaust gas re-circulation unit.
Furthermore, a battery may be provided in the coolant circulation system having the second radiator.
With the circulation apparatus for coolant in a vehicle of the present invention, a circulation quantity control device for controlling the quantity of coolant circulated to the respective apparatus to be cooled, may be provided between the apparatus to be cooled and the radiator.
With this coolant circulation apparatus, a quantity of coolant necessary for the respective apparatus to be cooled is circulated by the coolant quantity control devices. That is to say, the respective coolant quantity control devices distribute the coolant fed from the radiator, to the respective apparatus to be cooled.
For the coolant quantity control device, there is provided pumps respectively provided for example for the apparatus to be cooled.
Here in the case where coolant is circulated from one radiator to a plurality of apparatus to be cooled, there is the case where if one pump is stopped, then when the other pump is operating, the coolant is not supplied to the radiator but flows back to the other apparatus to be cooled, the pump for which is stopped. In this case, the coolant is not circulated between the radiator but is circulated between the apparatus to be cooled, the pump for which is stopped. To prevent this, the pump is not completely stopped even in the case where it is not necessary to cool the apparatus to be cooled with coolant, and is operated to the extent that the coolant does not flow back.
As a means for preventing reverse flow, then instead of the above, the installation of a non-return valve may be considered. However, this has the problem that when the coolant is flowing, the non-return valve causes flow resistance. If the reverse flow is prevented with a circulation quantity control device such as a pump as described above, this problem does not arise, and the energy loss of the pump can be restrained. That is to say, rather than providing the non return valve, the construction where reverse flow is prevented by the pump enables a smaller pump, with a reduction in vehicle weight.
Moreover, a coolant heating device may be provided for heating the coolant, and a coolant mixture of a high temperature coolant heated by the coolant heating device and a coolant of a lower temperature than the high temperature coolant may be circulated to the apparatus to be cooled.
As a coolant heating device there is an apparatus such as the engine which heats the coolant. For the low temperature coolant, there is for example coolant which has been cooled by the radiator, or coolant which has been heated by the apparatus to be cooled.
By mixing the high temperature coolant and the low temperature coolant, then a coolant of an optional temperature within a range of the temperatures can be produced. Temperature control is performed by adjusting the quantity of high temperature coolant and low temperature coolant which are mixed together. In this way, for example a constant temperature coolant is continuously circulated to the apparatus to be cooled (for example the lithium ion battery) so that the apparatus to be cooled can be maintained a constant temperature.